Silicone release coatings are widely used to render surfaces non-adherent. Non-adherent surfaces are necessary in the case of pressure-sensitive adhesives for easy transportation and storage prior to use of labels, decorative laminates, transfer tapes, etc. Likewise, non-adherent surfaces are desirable for food handling and industrial packaging.
There is a continuing need in the release coating industry to develop materials with "differential release" characteristics. In other words, there are wanted release coatings, the release of which may be adjusted to various levels as desired. With "differential release", premature release can be prevented while accounting for easy release when desired.
U.S. Pat. No. 4,448,815 discloses a heat curable release coating composition crosslinked by addition reaction in the presence of a platinum catalyst. There is no teaching as to a controlled release.
U.S. Pat. No. 4,576,999 discloses a UV radiation curable release coating composition crosslinked either through epoxy or acrylic functions. Again, there is no teaching as to a controlled release.
U.S. Ser. No. 171,498, filed Mar. 21, 1988, now U.S. Pat. No. 4,977,198, discloses the reaction by esterification of benzoyl compounds with epoxy functional silicone to produce a silicone polymer self-sensitized to UV radiation and having a modified release. Other methods to modify release are desirable, particularly methods with broader application to different chemistries.
U.S. Pat. No. 4,547,431 discloses UV radiation curable epoxy functional silicone further containing polyfunctional epoxy monomers. The additional monomers provide quantitative variable release. Again, other methods are desired to modify release, not specific to epoxy chemistry.
It is an object of the present invention to produce differential release silicone coatings.
It is a further object of the present invention to produce silicone polymers substituted to provide differential release.